1 /*
2 Generic support for BUG()
3
4 This respects the following config options:
5
6 CONFIG_BUG - emit BUG traps. Nothing happens without this.
7 CONFIG_GENERIC_BUG - enable this code.
8 CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG
9
10 CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable
11 (though they're generally always on).
12
13 CONFIG_GENERIC_BUG is set by each architecture using this code.
14
15 To use this, your architecture must:
16
17 1. Set up the config options:
18 - Enable CONFIG_GENERIC_BUG if CONFIG_BUG
19
20 2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON)
21 - Define HAVE_ARCH_BUG
22 - Implement BUG() to generate a faulting instruction
23 - NOTE: struct bug_entry does not have "file" or "line" entries
24 when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate
25 the values accordingly.
26
27 3. Implement the trap
28 - In the illegal instruction trap handler (typically), verify
29 that the fault was in kernel mode, and call report_bug()
30 - report_bug() will return whether it was a false alarm, a warning,
31 or an actual bug.
32 - You must implement the is_valid_bugaddr(bugaddr) callback which
33 returns true if the eip is a real kernel address, and it points
34 to the expected BUG trap instruction.
35
36 Jeremy Fitzhardinge <jeremy@goop.org> 2006
37 */
38 #include <linux/list.h>
39 #include <linux/module.h>
40 #include <linux/bug.h>
41 #include <linux/sched.h>
42
43 extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
44
45 #ifdef CONFIG_MODULES
46 static LIST_HEAD(module_bug_list);
47
48 static const struct bug_entry *module_find_bug(unsigned long bugaddr)
49 {
50 struct module *mod;
51
52 list_for_each_entry(mod, &module_bug_list, bug_list) {
53 const struct bug_entry *bug = mod->bug_table;
54 unsigned i;
55
56 for (i = 0; i < mod->num_bugs; ++i, ++bug)
57 if (bugaddr == bug->bug_addr)
58 return bug;
59 }
60 return NULL;
61 }
62
63 int module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
64 struct module *mod)
65 {
66 char *secstrings;
67 unsigned int i;
68
69 mod->bug_table = NULL;
70 mod->num_bugs = 0;
71
72 /* Find the __bug_table section, if present */
73 secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
74 for (i = 1; i < hdr->e_shnum; i++) {
75 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
76 continue;
77 mod->bug_table = (void *) sechdrs[i].sh_addr;
78 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
79 break;
80 }
81
82 /*
83 * Strictly speaking this should have a spinlock to protect against
84 * traversals, but since we only traverse on BUG()s, a spinlock
85 * could potentially lead to deadlock and thus be counter-productive.
86 */
87 list_add(&mod->bug_list, &module_bug_list);
88
89 return 0;
90 }
91
92 void module_bug_cleanup(struct module *mod)
93 {
94 list_del(&mod->bug_list);
95 }
96
97 #else
98
99 static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
100 {
101 return NULL;
102 }
103 #endif
104
105 const struct bug_entry *find_bug(unsigned long bugaddr)
106 {
107 const struct bug_entry *bug;
108
109 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
110 if (bugaddr == bug->bug_addr)
111 return bug;
112
113 return module_find_bug(bugaddr);
114 }
115
116 enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
117 {
118 const struct bug_entry *bug;
119 const char *file;
120 unsigned line, warning;
121
122 if (!is_valid_bugaddr(bugaddr))
123 return BUG_TRAP_TYPE_NONE;
124
125 bug = find_bug(bugaddr);
126
127 printk(KERN_EMERG "------------[ cut here ]------------\n");
128
129 file = NULL;
130 line = 0;
131 warning = 0;
132
133 if (bug) {
134 #ifdef CONFIG_DEBUG_BUGVERBOSE
135 file = bug->file;
136 line = bug->line;
137 #endif
138 warning = (bug->flags & BUGFLAG_WARNING) != 0;
139 }
140
141 if (warning) {
142 /* this is a WARN_ON rather than BUG/BUG_ON */
143 if (file)
144 printk(KERN_ERR "Badness at %s:%u\n",
145 file, line);
146 else
147 printk(KERN_ERR "Badness at %p "
148 "[verbose debug info unavailable]\n",
149 (void *)bugaddr);
150
151 show_regs(regs);
152 return BUG_TRAP_TYPE_WARN;
153 }
154
155 if (file)
156 printk(KERN_CRIT "kernel BUG at %s:%u!\n",
157 file, line);
158 else
159 printk(KERN_CRIT "Kernel BUG at %p "
160 "[verbose debug info unavailable]\n",
161 (void *)bugaddr);
162
163 return BUG_TRAP_TYPE_BUG;
164 }
165
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